Hiccups are a complex motor action, during which the brain coordinates the sudden contraction of the diaphragm muscles that help you breathe in. Just after the contraction, the vocal chords close off, creating the "hic" sound. Although hiccups are unintentional movements, known as spasms, many triggers can cause this complex reaction. You are most likely to get hiccups as a result of your stomach expanding or becoming distended. This can happen if you overeat, drink carbonated beverages, drink excessive amounts of alcohol, or smoke. When enlarged, your stomach may irritate your phrenic nerve, which is the nerve that innervates your diaphragm. The nerve irritation is thought to act as a trigger for the brain to initiate hiccups. Eating spicy foods, a sudden change in temperature, and excitement or stress are also common causes of the hiccups.
Sometimes hiccups are caused by a more serious trigger, such as nerve damage or a problem with the central nervous system. Gastroesophageal reflux can irritate the phrenic nerve, causing hiccups. Reflux is commonly caused by eating spicy foods and some medications can cause reflux as a side effect. A tumor, cyst or goiter in your neck may also be the cause of persistent hiccups, as well as a chest or throat infection. Disorders that may affect your central nervous system and cause hiccups are stroke, multiple sclerosis, tumors, meningitis, encephalitis or injury to the brain as a result of trauma. Certain diseases, such as kidney failure and diabetes, can also cause the hiccups. If your hiccups persist for more than 48 hours it is important to see a doctor, as there may be a serious reason behind your hiccups.